For instance, being a crater rim, I would not expect neat layering; I find it difficult to explain the "ringing" about Cape York in a manner other than waterlines. I see at least 4 major levels. I'd love to see this in 3D.

At the upper end there is a steep wedge-shaped incision (see highlighted image below). Note that the wedge cuts through at least two of the "rings", and appears to project a fair distance to the north (?). I'm inclined interpret it as a landslide, but having difficulty with the mechanism; I suppose it could be an eroded fracture. In the highlighted image, the point of the wedge has its origin between the highlighted green and blue rings; this region is very smooth, such that I am tempted to interpret it as the remains of a beach. Sheer speculation, of course Overall, the northern end of Cape York looks the most interesting, and I very much look forward to a pic from Oppy looking down on the Wedge.

Those rings - don't think waterlines, the topography doesn't work - it's on a slope. Think instead: a very ancient crater rim that has had multiple layers of sediment (ejecta, windblown sand or dust, volcanic ash, etc.) deposited, cemented by fluctuating ground waters, and then differentially eroded. We see the end product of multiple depositional and erosional events.

This sounds sensible, with the caveat that slopes may be historically variable. You're almost certainly correct, though with the presence of groundwater presumed historically in the region where Oppy has heretofore traversed, and with (at least the interior of) Endeavour being dramatically lower, I would hesitate to definitively rule-out surface water until we get some on-the-ground verification. Aside from that, I'm still really intrigued by the Wedge.

At the upper end there is a steep wedge-shaped incision (see highlighted image below).

With regard to the "wedge-shaped" cut...if you ask me I see a sinuous channel above the wedge and slightly east that you can follow up to the two depressions at the top of the formation. I've been staring at this for months and (call me crazy, go ahead) I can imagine the whole region covered in a slowly receding body of water.

The rim of Endeavour would at first have been something like a circular archipelago. As the water level receded you could see how two lagoons might have formed in those depressions. They might later have become lakes or ponds as the water receded almost to the base of Cape York. If something caused those those lagoons to drain suddenly to the north, you would get a meandering stream on the slope, but when it reached the steeper ledge of the apron it would have been a more energetic stream or even a waterfall that would have eroded backward creating the wedge.

You can also see how the channel becomes broader at the base of the cut where the slope becomes more gradual, creating something akin to an alluvial fan or a mini-delta. If you follow on past the wedge you can almost see a small round low lying basin next to a crater where the water might have collected before evaporating or settling into an underground water table.

Somewhere we have already had a nice stratigrapher's resume of these features but the interpretation there was that the 'waterfall stream' arrived at the wedge after flowing round the E flank of Cape York where there is indeed what looks like a narrow channel where the hill slope meets the 'beach' platform. Can I find the post? No.

Anyone remember it? We could use a link back to that, and the discussion it was part of.

The rim of Endeavour is really eroded and the meridiani hematite sedimentary beds fill much of the interior floor. Since the crater is lower than the playa region examined to date is it beyond the bounds of possibility that Endeavour region did in fact have a shallow lake?

Any possibilities are, well, possible. We'll need to see what the nature (stratigraphy, petrology and depositional environment) of the bedrock outcrops is as we travel downhill. Already we see subtle changes and the gross appearance from orbital imagery changes towards the East.

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